feat: mail service

mail/internal/api/internalhttp/observability.go

@@ -0,0 +1,114 @@
+package internalhttp
+
+import (
+	"log/slog"
+	"net/http"
+	"time"
+
+	"galaxy/mail/internal/logging"
+	"galaxy/mail/internal/telemetry"
+
+	"go.opentelemetry.io/otel/attribute"
+)
+
+type edgeOutcome string
+
+const (
+	edgeOutcomeSuccess  edgeOutcome = "success"
+	edgeOutcomeRejected edgeOutcome = "rejected"
+	edgeOutcomeFailed   edgeOutcome = "failed"
+)
+
+func instrumentRoute(route string, logger *slog.Logger, telemetryRuntime *telemetry.Runtime, next http.Handler) http.Handler {
+	if logger == nil {
+		logger = slog.Default()
+	}
+
+	return http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
+		startedAt := time.Now()
+		recorder := &observedResponseWriter{
+			ResponseWriter: writer,
+			statusCode:     http.StatusOK,
+		}
+
+		next.ServeHTTP(recorder, request)
+
+		duration := time.Since(startedAt)
+		outcome := outcomeFromStatusCode(recorder.statusCode)
+		attrs := []attribute.KeyValue{
+			attribute.String("route", route),
+			attribute.String("method", request.Method),
+			attribute.String("edge_outcome", string(outcome)),
+		}
+		if recorder.errorCode != "" {
+			attrs = append(attrs, attribute.String("error_code", recorder.errorCode))
+		}
+		if telemetryRuntime != nil {
+			telemetryRuntime.RecordInternalHTTPRequest(request.Context(), attrs, duration)
+		}
+
+		logArgs := []any{
+			"component", "internal_http",
+			"transport", "http",
+			"route", route,
+			"method", request.Method,
+			"status_code", recorder.statusCode,
+			"duration_ms", float64(duration.Microseconds()) / 1000,
+			"edge_outcome", string(outcome),
+		}
+		if recorder.errorCode != "" {
+			logArgs = append(logArgs, "error_code", recorder.errorCode)
+		}
+		logArgs = append(logArgs, logging.TraceAttrsFromContext(request.Context())...)
+
+		switch outcome {
+		case edgeOutcomeSuccess:
+			logger.Info("internal request completed", logArgs...)
+		case edgeOutcomeFailed:
+			logger.Error("internal request failed", logArgs...)
+		default:
+			logger.Warn("internal request rejected", logArgs...)
+		}
+	})
+}
+
+type observedResponseWriter struct {
+	http.ResponseWriter
+
+	statusCode  int
+	errorCode   string
+	wroteHeader bool
+}
+
+func (writer *observedResponseWriter) WriteHeader(statusCode int) {
+	if writer.wroteHeader {
+		return
+	}
+
+	writer.statusCode = statusCode
+	writer.wroteHeader = true
+	writer.ResponseWriter.WriteHeader(statusCode)
+}
+
+func (writer *observedResponseWriter) Write(payload []byte) (int, error) {
+	if !writer.wroteHeader {
+		writer.WriteHeader(http.StatusOK)
+	}
+
+	return writer.ResponseWriter.Write(payload)
+}
+
+func (writer *observedResponseWriter) SetErrorCode(code string) {
+	writer.errorCode = code
+}
+
+func outcomeFromStatusCode(statusCode int) edgeOutcome {
+	switch {
+	case statusCode >= 500:
+		return edgeOutcomeFailed
+	case statusCode >= 400:
+		return edgeOutcomeRejected
+	default:
+		return edgeOutcomeSuccess
+	}
+}